High capacity optical waveguide fiber

ABSTRACT

Disclosed is an optical waveguide fiber that simultaneously exhibits large effective area and good resistance to bend induced attenuation, as measured by any of the tests known in the art. The cut off wavelength is controlled to allow single mode operation over a wavelength range that extends from about 1340 nm to 1650 nm. The optical waveguide fiber refractive index profile is simple in design allowing cost effective manufacture.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. §119(e) of U.S. Provisional Application Serial No. 60/332,391 filed onNov. 15, 2001.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] An optical waveguide fiber is disclosed herein for high capacitytelecommunications systems and particularly an optical waveguide fibercombining large effective area and resistance to bend inducedattenuation.

[0004] 2. Technical Background

[0005] Optical waveguide fibers designed for transmission of greaterinformation capacity over long distances, preferably without use ofelectronic regenerators, typically reduce certain types of non-linearinteractions of the signal by providing high effective area. Inaddition, the signal degrading effect commonly called four wave or fourphoton mixing, an effect that occurs in communications systems usingwavelength division signal multiplexing, can be counteracted by controlof the optical waveguide fiber total dispersion over the operatingwavelength range. That is, the total dispersion is made to be non-zeroover the operating wavelength range, thus altering the phaserelationship among the signals in such a way that they do not interfere.

[0006] Through use of dispersion compensation strategies, a highcapacity optical waveguide fiber can have a greater total dispersionmagnitude over the operating window of a communication system. Thus, thedesign limitations are loosened somewhat, allowing a refractive indexprofile researcher to relax total dispersion requirements whileimproving other key fiber properties such as attenuation and resistanceto bend induced attenuation.

[0007] An additional important factor in refractive index profile designof high capacity optical waveguide fibers is the simplicity of theprofile as simplicity of design relates to manufacturing cost. Forexample, a core region that provides the desired properties but hasfewer significant changes in refractive index along a radius will ingeneral be easier to manufacture.

[0008] The present invention addresses the need for high capacityoptical waveguide fiber designs which have a simpler refractive indexprofile structure and provide high effective area while maintaining lowattenuation and providing excellent resistance to bend inducedattenuation.

DEFINITIONS

[0009] The following definitions are in accord with common usage in theart.

[0010] The refractive index profile is the relationship betweenrefractive index or relative refractive index (percent) and waveguidefiber radius.

[0011] A segmented core is one that is divided into at least a first anda second waveguide fiber core portion or segment. Each portion orsegment is located along a particular radial length, is substantiallysymmetric about the waveguide fiber centerline, and has an associatedrefractive index profile.

[0012] The radii of the segments of the core are defined in terms of therespective refractive indexes at respective beginning and end points ofthe segments. The definitions of the radii used herein are set forth inthe figures and the discussion thereof.

[0013] Total dispersion, sometimes called chromatic dispersion, of awaveguide fiber is the sum of the material dispersion, the waveguidedispersion, and the inter-modal dispersion. In the case of single modewaveguide fibers the inter-modal dispersion is zero.

[0014] The sign convention generally applied to the total dispersion isas follows. Total dispersion is said to be positive if shorterwavelength signals travel faster than longer wavelength signals in thewaveguide. Conversely, in a negative total dispersion waveguide, signalsof longer wavelength travel faster.

[0015] The effective area is

[0016] A_(eff)=2π(∫E² r dr)²/(∫E⁴ r dr), where the integration limitsare 0 to ∞, and E is the electric field associated with light propagatedin the waveguide.

[0017] The relative refractive index percent, Δ%=100×(n_(i) ²−n_(c)²)/2n_(i) ², where n_(i) is the maximum refractive index in region i,unless otherwise specified, and n_(c) is the average refractive index ofthe cladding region. In those cases in which the refractive index of asegment is less than the average refractive index of the claddingregion, the relative index percent is negative and is calculated at thepoint at which the relative index in most negative unless otherwisespecified. A positive relative index percent occurs where the refractiveindex is greater than the average refractive index of the cladding.

[0018] The term α-profile refers to a refractive index profile,expressed in terms of Δ(b)%, where b is radius, which follows theequation, Δ(b)%=Δ(b₀₎₍1−[|b−b₀|/(b₁−b₀)]^(α)), where b₀ is the point atwhich Δ(b)% is maximum, b₁ is the point at which α(b)% is zero, and b isin the range b_(i)≦b≦b_(f), where delta is defined above, b_(i) is theinitial point of the α-profile, b_(f) is the final point of theα-profile, and α is an exponent which is a real number.

[0019] The bend resistance of a waveguide fiber is expressed as inducedattenuation under prescribed test conditions. Bend induced attenuationis also called bend loss herein. A bend test referenced herein is thepin array bend test that is used to compare relative resistance ofwaveguide fiber to bending. To perform this test, attenuation loss ismeasured for a waveguide fiber with essentially no induced bending loss.The waveguide fiber is then woven in a serpentine path through the pinarray and attenuation again measured. The loss induced by bending is thedifference between these two measured attenuation values expressed indB. The pin array is a set of ten cylindrical pins arranged in a singlerow and held in a fixed vertical position on a flat surface. The pinspacing is 5 mm, center to center. The pin diameter is 0.67 mm. Duringtesting, sufficient tension is applied to make the serpentine wovenwaveguide fiber conform to the portions of the pin surface at whichthere is contact between fiber and pin.

[0020] Another bend test referenced herein is the lateral load wire meshtest. In this test a prescribed length of waveguide fiber is placedbetween two flat plates. A #70 wire mesh is attached to one of theplates. A known length of waveguide fiber is sandwiched between theplates and a reference attenuation is measured while the plates arepressed together with a force of 30 newtons. A 70 newton force is thenapplied to the plates and the increase in attenuation is measured andexpressed in dB/m. This increase in attenuation is the lateral loadattenuation (or lateral load bend loss) of the waveguide.

[0021] A further test of the bend resistance of a waveguide fiber is onein which the fiber is wrapped a specified number of turns about amandrel of a specified diameter. In each test condition the bend inducedattenuation is expressed in units of dB/m, the length being determinedby the number of turns of fiber and the mandrel diameter. The mandrelwrap test referenced herein is one in which induced attenuation ismeasured for 1 turn of waveguide fiber around a 20 mm diameter mandrel.

SUMMARY OF THE INVENTION

[0022] In one aspect, an optical waveguide fiber is disclosed hereinwhich includes a central core region surrounded by and in contact with aclad layer. The central core region has a refractive index profile, aradius, and a centerline. The central core region has a portion with arefractive index profile configured to provide a local minimum relativerefractive index percent on or near the centerline which is a fractionof the maximum relative refractive index percent of the central coreregion. In particular, the fraction formed by the ratio of the localminimum relative refractive index percent on or near centerline to themaximum value of relative refractive index percent in the central coreregion is in the range from 0.65 to 1.0. This fraction, together withthe value of central core radius and maximum relative refractive indexpercent are chosen to provide an optical waveguide fiber having aneffective area not less than 115 μm² at 1550 nm, a 20 mm mandrel wrapbend loss at 1550 nm not greater than 25 dB/m, and a lateral load wiremesh bend loss at 1550 nm not greater than 1.5 dB/m, preferably notgreater than 0.5 dB/m. Advantageously, the pin array bend loss at 1550nm is not greater than 1 dB/m. The 20 mm mandrel wrap bend loss ispreferably not greater than 20 dB/m, and more preferably not greaterthan 10 dB/m.

[0023] The fraction preferably lies in the range from 0.75 to 0.85.

[0024] In an embodiment of the optical waveguide fiber disclosed herein,the refractive index profile parameters are selected to further providean attenuation at 1550 nm less than or equal to 0.22 dB/km, zerodispersion wavelength no greater than 1400 nm, polarization modedispersion not greater than 0.06 ps/km^(1/2), and cabled cut offwavelength no greater than 1500 nm. The attenuation at 1550 nm ispreferably less than 0.20 dB/km, more preferably less than 0.19 dB/km.

[0025] In a further embodiment of the optical waveguide fiber disclosedherein, the maximum relative refractive index percent of the centralcore region is reached at a radius not less than 0.25 of the centralcore radius. The central core radius of this embodiment has a range from6 μm to 9 μm and preferably a range from 6.5 μm to 7.5 μm.

[0026] In this first aspect, the maximum value of relative refractiveindex percent has a range from 0.25% to 0.45% and preferably a rangefrom 0.28% to 0.35%.

[0027] In another embodiment of this first aspect, the optical waveguidefiber disclosed herein has a central core region that exhibits arelative refractive index percent that rises monotonically from itscenterline value to its maximum value. The local minimum relativerefractive index percent on or near the centerline in the central coreregion in this embodiment has a range from 0.2% to 0.3%.

[0028] In a second aspect, the optical waveguide fiber disclosed hereinincludes a central core region and an annular region of negativerelative refractive index percent located between the central coreregion and the surrounding clad layer. Preferably, tne clad layer isadjacent to the annular region, and the annular region is adjacent tothe central core region. The negative relative refractive index percentof the annular region can be achieved by adding an index reducing dopantto the annular region or by adding an index increasing dopant to theclad layer. These alternatives are in accord with the definition ofnegative relative refractive index percent stated above. Preferably, thecentral core region has a radius in the range from 7 μm to 9.5 μm. Also,preferably the annular negative relative refractive index percent regionhas inner radius equal to the central core radius, an outside radius inthe range from 14 μm to 18 μm, and a minimum relative refractive indexpercent in the range from −0.05% to −0.15%.

[0029] The effective area is not less than 120 μm, preferably is notless than 130 μm, more preferably not less than 140 μm², and mostpreferably not less than 150 μm². In addition, the bend resistance issuch that one turn of the fiber about a 20 mm diameter mandrel inducesan attenuation at 1550 nm of less than 25 dB/m, and preferably less than20 dB/m, and more preferably less than 10 dB/m.

[0030] In each of the embodiments set forth above, the OH⁻ content ofthe optical waveguide fiber is preferably controlled to a valuesufficiently low to enable operation of the waveguide in a wavelengthregion including the range 1380 nm to 1390 nm.

[0031] Additional features and advantages of the invention will be setforth in the detailed description which follows, and in part will bereadily apparent to those skilled in the art from that description orrecognized by practicing the invention as described herein, includingthe detailed description which follows, the claims, as well as theappended drawings.

[0032] It is to be understood that both the foregoing generaldescription and the following detailed description are merely exemplaryof the invention, and are intended to provide an overview or frameworkfor understanding the nature and character of the invention as it isclaimed. The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate various embodimentsof the invention, and together with the description serve to explain theprinciples and operation of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 is a refractive index profile plotted in relativerefractive index percent versus radius for an optical waveguide fiber asdisclosed herein.

[0034]FIGS. 2 and 3 show graphs of relative refractive index percentversus radius of comparative examples.

[0035]FIG. 4 is a refractive index profiled plotted in relativerefractive index percent versus radius for another embodiment of anoptical waveguide fiber as disclosed herein.

[0036]FIG. 5 is a refractive index profiled plotted in relativerefractive index percent versus radius for yet another embodiment of anoptical waveguide fiber as disclosed herein.

[0037]FIG. 6 is a refractive index profiled plotted in relativerefractive index percent versus radius for still another embodiment ofan optical waveguide fiber as disclosed herein.

[0038]FIG. 7 is a refractive index profiled plotted in relativerefractive index percent versus radius for another embodiment of anoptical waveguide fiber as disclosed herein.

[0039]FIG. 8 is a refractive index profiled plotted in relativerefractive index percent versus radius for yet another embodiment of anoptical waveguide fiber as disclosed herein.

DETAILED DESCRIPTION OF THE INVENTION

[0040] Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.An exemplary embodiment of the optical waveguide fiber disclosed hereinis shown in FIG. 1, represented by a graph of relative refractive indexpercent versus radius of the optical waveguide fiber. The central coreregion of the optical fiber has a portion with a relative refractiveindex percent that has a lower value or local minimum 2 on or near thecenterline and then increases until reaching the maximum value ofrelative refractive index percent 4 of the central core region at radius6. The relative refractive index percent preferably remains at itsmaximum value for another portion of the central core region until therelative refractive index percent decreases in magnitude until reachingthe clad layer at radius 8.

[0041] Although the increase in relative refractive index percent fromits value at or near the centerline to that at radius 6 is shown as amonotonic increase in FIG. 1, it will be understood that the increasingprofile portion can take on a variety of shapes while retainingproperties in accord with the optical waveguide fiber disclosed herein.For example, the profile shape between relative refractive index percentpoints 2 and 4 can be a step, a series of steps, or smooth curves havingdifferent degrees of concavity or convexity.

[0042] The relative refractive index percent profile in accord with theoptical waveguide fiber disclosed herein provides a large effective areatogether with an excellent resistance to bend induced attenuation. Thebend resistance is characterized by the bend tests set forth above,although other bend tests, for example those using different screen meshsize in the lateral load test, can be used. These features are enhancedwhen combined in an optical waveguide fiber that further ischaracterized by a low water peak over the range of wavelengths 1380 nmto 1386 nm.

[0043] Over this range of wavelengths, the water peak in the attenuationcurve of an optical waveguide fiber can be reduced to a value notgreater than about 0.5 dB/km, preferably not greater than about 0.4dB/km, and most preferably not greater than about 0.35 dB/km.

[0044] Methods of producing low water peak optical fiber can be found inU.S. application Ser. No. 09/722,804 filed Nov. 27, 2001, U.S.application Ser. No. 09/547,598 filed Apr. 11, 2000, U.S. ProvisionalApplication Serial No. 60/258,179 filed Dec. 22, 2000, and U.S.Provisional Application Serial No. 60/275,015 filed Feb. 28, 2001, thecontents of each being hereby incorporated by reference. Generally, themethod set forth in the incorporated documents includes the steps ofdrying the soot preform using a gas such as chlorine and thenmaintaining the soot in its dry state by isolating the essentially OH⁻free (dry) soot from contact with any source of OH⁻ ions, hydrogen orhydrogen containing compound. The soot can be deposited using any of theseveral methods known in the art, for example, outside vapor deposition,modified vapor deposition, or vertical vapor deposition. A preferredmethod of isolating the dried soot from sources of OH⁻ ions, hydrogen orhydrogen containing compounds is through use of deuterated glassarticles as containing means for the dried soot. In those sootdeposition processes that result in a soot preform having a centerlinehole, deuterated glass plugs can be used to seal the centerline, therebypreventing re-wetting of the dried soot.

[0045] An example of a method of deuterating a glass body that will beproximate the dried soot, acting for example as a seal or the walls of achamber, the glass body is exposed to 5% deuterium in a heliumatmosphere at 1 atm at about 1000° C. for about 24 hours. As analternative the glass body can be exposed to 3% deuterium in a nitrogenatmosphere at 1 atm at about 1000° C. for about 24 hours.

[0046] Advantageous features of the optical waveguide fiber disclosedherein are illustrated by the following examples and comparativeexamples. In the exemplified embodiments below, the modeled parametricvalues of the optical waveguide fiber have been verified throughmeasurement of fibers manufactured in accord with the embodiment.

EXAMPLE 1

[0047] Referring to FIG. 1, the central core region has a portion with alocal minimum relative refractive index percent 2 on or near centerlineequal to about 0.25%, and the central core region maximum relativerefractive index percent 4 is about 0.30% and is located at a radius 6of about 3.64 μm, and the core radius 8 is about 7.1 μm. Table 1 givesthe modeled optical properties of the optical waveguide fiber having acore region in accord with FIG. 1. TABLE 1 Total Dispersion at 1550 nm(ps/nm-km) 20.86 Dispersion Slope at 1550 nm (ps/nm²-km) 0.06Attenuation at 1550 nm (dB/km) 0.188 Effective Area (μm²) 126.0 LateralLoad Bend Loss (dB/m) 0.04 Pin Array Bend Loss (dB) 0.05 Δ_(1, LM)(%)0.25 R_(1,LM)(μm) 0 Δ_(1, MAX)(%) 0.30$\frac{\Delta_{1,{LM}}}{\Delta_{1,{MAX}}}$

0.83 R_(1,MAX)(μm) 3.64 R₁(μm) 7.1 $\frac{R_{1,{MAX}}}{R_{1}}$

0.51 $\frac{R_{1,{LM}}}{R_{1}}$

0 R_(1,MAX) − R_(1,LM)(μm) 3.64$\frac{\Delta_{1,{MAX}} - \Delta_{1,{LM}}}{R_{1,{MAX}} - R_{1,{LM}}}\left( {\% \text{-}{\mu m}^{- 1}} \right)$

0.0137

[0048] Two fibers were manufactured having a core region in accord withFIG. 1. The measured results are given in Table 2. TABLE 2 Fiber 1 Fiber2 Total Dispersion at 1550 nm 19.9 20.1 (ps/nm-km) Dispersion Slope at1550 nm 0.061 0.060 (ps/nm²-km) Effective Area (μm²) 119 125 20 mmMandrel (dB/m) 17 6 Pin Array Bend Loss (dB) 0.4 5.2 Cabled Cutoff (nm)1341 1482

[0049] A comparison of Tables 1 and 2 shows good agreement between therespective modeled and measured results. Table 2 shows that themanufactured fiber has high effective area, low pin array bend inducedloss, and low mandrel wrap bend induced loss. These properties allow foroperation of a high performance telecommunication system.

[0050] The low cabled cut off value of the optical waveguide fibermanufactured in accord with the invention allows a high performancesingle mode telecommunication system to operate over an extendedwavelength range, preferably a range spanning 1340 nm to 1650 nm.

COMPARATIVE EXAMPLE 2

[0051] An optical waveguide fiber having a relative refractive indexpercent core profile in accord with FIG. 2 was modeled to predictoptical properties. This profile exhibits a deeper depression or lowerlocal minimum on centerline with a relative refractive index percent ofabout 0.15%, and the radius at which the maximum relative refractiveindex percent is reached at about 4 μm, which occurs further radiallyoutward compared to Example 1. The modeled properties are given in Table3. TABLE 3 Total Dispersion at 1550 nm (ps/nm-km) 20.73 Dispersion Slopeat 1550 nm (ps/nm²-km) 0.06 Attenuation at 1550 nm (dB/km) 0.190Effective Area (μm²) 143.75 Lateral Load Bend Loss (dB/m) 8.95 Pin ArrayBend Loss (dB) 8.89 Δ_(1,LM)(%) 0.15 R_(1,LM)(μm) 0 Δ_(1,MAX)(%) 0.3$\frac{\Delta_{1,{LM}}}{\Delta_{1,{MAX}}}$

0.5 R_(1,MAX)(μm) 4 R₁(μm) 7.1 $\frac{R_{1,{MAX}}}{R_{1}}$

0.56 $\frac{R_{1,{LM}}}{R_{1}}$

R_(1,MAX) − R_(1,LM)(82 m) 4$\frac{\Delta_{1,{MAX}} - \Delta_{1,{LM}}}{R_{1,{MAX}} - R_{1,{LM}}}\left( {\% \text{-}{\mu m}^{- 1}} \right)$

0.0375

[0052] A comparison of Tables 1 and 3 show that although effective areais larger for the central core region in accord with FIG. 2, the bendinduced attenuation has increased dramatically. The performance of theoptical waveguide fiber of example 1 can be expected to exhibit superiorperformance in a telecommunication system in comparison to the opticalwaveguide fiber of comparative example 2.

COMPARATIVE EXAMPLE 3

[0053] An optical waveguide fiber having a relative refractive indexpercent core profile in accord with FIG. 3 was modeled to predictoptical properties. This profile exhibits no depression on or nearcenterline and is essentially a step index core having an outside radiusof about 7.1 μm, equal to that of the profile of FIG. 1 in accord withthe disclosure herein. The modeled properties are given in Table 4.TABLE 4 Total Dispersion at 1550 nm (ps/nm-km) 20.78 Dispersion Slope at1550 nm (ps/nm²-km) 0.06 Attenuation at 1550 nm (dB/km) 0.187 EffectiveArea (μm²) 120.57 Lateral Load Bend Loss (dB/m) 2.26 Pin Array Bend Loss(dB) 1.15 Δ_(1, MAX) (%) 0.3 R₁ (μm) 7.1

[0054] A comparison of Tables 1 and 4 show that effective area issmaller for the central core region in accord with FIG. 3 and the bendinduced attenuation is a factor of about 50 greater than that of theoptical waveguide fiber made in accord with FIG. 1 as disclosed herein.The performance of the optical waveguide fiber of example 1 can beexpected to exhibit superior performance in a telecommunication systemin comparison to the optical waveguide fiber of comparative example 3.

EXAMPLE 4

[0055] In a second aspect, certain properties of the optical waveguidefiber disclosed herein can be enhanced by including an annular region oflower refractive index surrounding the central core region in accordancewith the optical waveguide fiber disclosed herein. Referring to theexample in FIG. 4, the local minimum relative refractive index percentof the central core region on or near the centerline 2 is about 0.25%,and the maximum relative refractive index percent of the central coreregion is about 0.30% and is located at a radius 6 of about 4.0 μm. Thecentral core radius 8 is about 7.7 μm. A negative relative refractiveindex percent annular region 14 extends from the end of the central coreregion to a radius 12 of about 16.6 μm. The shape of the negativerelative refractive index percent annular region shown in FIG. 4 is arounded step having a most negative relative refractive index percent ofabout 0.09% (i.e. a minimum relative refractive index percent of −0.09%for the annular region). It will be understood that the shape of theannular region of negative relative refractive index percent can take onshapes other than that of the illustrated rounded step while preservingthe desired properties of the optical waveguide fiber disclosed herein.For example, the annular region can have a trapezoidal shape or can havean α-profile with α in the range from 0.1 to 20.

[0056] Table 5 gives the modeled functional properties of the opticalwaveguide fiber having a central core region and annular region inaccord with FIG. 4. TABLE 5 Total Dispersion at 1550 nm (ps/nm-km) 22.26Dispersion Slope at 1550 nm (ps/nm²-km) 0.06 Attenuation at 1550 nm(dB/km) 0.188 Effective Area (μm²) 136.93 Lateral Load Bend Loss (dB/m)0.24 Pin Array Bend Loss (dB) 0.21

[0057] The addition of the annular region of negative relativerefractive index percent surrounding the central core region allows anincrease in effective area by about 10% while maintaining excellentresistance to bend induced attenuation.

EXAMPLE 5

[0058] An optical fiber was manufactured having a central core region,an annular region, and cladding similar to that shown in FIG. 4. Themeasured refractive index profile of the manufactured fiber is shown bythe plot of relative refractive index percent versus radius in FIG. 5.The local minimum relative refractive index percent of the central coreregion on or near the centerline 2 is about 0.245% at a radius of about0.24 μm, and the maximum relative refractive index percent of thecentral core region is about 0.30% and is located at a radius 6 of about5.0 μm. The central core radius 8, i.e. where the relative refractiveindex reaches 0%, is about 7.6 μm. A negative relative refractive indexpercent annular region 14 extends from the end of the central coreregion to a radius 12 of about 15.4 μm. The negative relative refractiveindex percent annular region shown in FIG. 5 has a minimum negativerelative refractive index percent of about 0.12% (i.e. a minimumrelative refractive index of about −0.12%) at a radius of about 13.4 μm.It will be understood that the shape of the annular region of negativerelative refractive index percent can take on shapes other than thatillustrated

[0059] The measured results of the optical fiber of FIG. 5 are given inTable 6. TABLE 6 Total Dispersion at 1550 nm (ps/nm-km) 20.50 DispersionSlope at 1550 nm (ps/nm²-km) 0.061 Effective Area (μm²) 137.0 20 mmMandrel (dB/m) 6 Pin Array Bend Loss (dB) 5.8 Cabled Cutoff (nm) 1480Δ₁,LM(%) 0.245 R_(1,LM)(μm) 0.24 Δ_(1,MAX)(%) 0.30$\frac{\Delta_{1,{LM}}}{\Delta_{1,{MAX}}}$

0.82 R_(1,MAX)(μm) 5.0 R₁(μm) 7.6 $\frac{R_{1,{MAX}}}{R_{1}}$

0.66 $\frac{R_{1,{LM}}}{R_{1}}$

0.03 R_(1,MAX) − R_(1,LM)(μm) 4.76 Δ_(2,MIN)(%) −0.12 R_(2,MIN)(μm) 13.4R₂(μm) 15.4 $\frac{R_{2}}{R_{1}}$

2.03$\frac{\Delta_{1,{MAX}} - \Delta_{1,{LM}}}{R_{1,{MAX}} - R_{1,{LM}}}\left( {\% \text{-}{\mu m}^{- 1}} \right)$

0.0116

EXAMPLE 6

[0060] An optical fiber was manufactured having a central core region,an annular region, and cladding. The measured refractive index profileof the manufactured fiber is shown by the plot of relative refractiveindex percent versus radius in FIG. 6. The local minimum relativerefractive index percent of the central core region on or near thecenterline 2 is about 0.256% at a radius of about 0.62 μm, and themaximum relative refractive index percent of the central core region isabout 0.308% and is located at a radius 6 of about 5.2 μm. The centralcore radius 8, i.e. where the relative refractive index reaches 0%, isabout 7.3 μm. A negative relative refractive index percent annularregion 14 extends from the end of the central core region to a radius 12of about 18.1 μm. The negative relative refractive index percent annularregion shown in FIG. 6 has a minimum negative relative refractive indexpercent of about 0.136% (i.e. a minimum relative refractive index ofabout −0.136%) at a radius of about 15.5 μm. It will be understood thatthe shape of the annular region of negative relative refractive indexpercent can take on shapes other than that illustrated

[0061] The measured results of the optical fiber of FIG. 6 are given inTable 7. TABLE 7 Total Dispersion at 1550 nm (ps/nm-km) 21.3 DispersionSlope at 1550 nm (ps/nm²-km) 0.065 Effective Area (μm²) 148.0 Pin ArrayBend Los (dB) 0.96 Cabled Cutoff (nm) 1340 Δ_(1,LM)(%) 0.256R_(1,LM)(μm) 0.62 Δ_(1,MAX)(%) 0.308$\frac{\Delta_{1,{LM}}}{\Delta_{1,{MAX}}}$

0.83 R_(1,MAX)(μm) 5.2 R₁(μm) 7.3 $\frac{R_{1,{MAX}}}{R_{1}}$

0.71 $\frac{R_{1,{LM}}}{R_{1}}$

0.08 R_(1,MAX) − R_(1,LM)(μm) 4.58 Δ_(2,MIN)(%) −0.136 R_(2,MIN)(μm)15.5 R₂(μm) 18.1 $\frac{R_{2}}{R_{1}}$

2.4$\frac{\Delta_{1,{MAX}} - \Delta_{1,{LM}}}{R_{1,{MAX}} - R_{1,{LM}}}\left( {\% \text{-}{\mu m}^{- 1}} \right)$

0.0114 Mode Field Diameter, MFD (μm) 13.05 Bend Loss 32 mm Mandrel, 1turn, @1550 0.03 nm (dB/m) Bend Loss 32 mm Mandrel, 1 turn, @1610 0.27nm (dB/m) Attenuation @ 1310 nm (dB/km) 0.333 Attenuation @ 1380 nm(dB/km) 0.308 Attenuation @ 1550 nm (dBlkm) 0.187 Attenuation @ 1610 nm(dB/km) 0.192 Length (km) 8.01

EXAMPLE 7

[0062] An optical fiber was manufactured having a central core region,an annular region, and cladding. The measured refractive index profileof the manufactured fiber is shown by the plot of relative refractiveindex percent versus radius in FIG. 7. The local minimum relativerefractive index percent of the central core region on or near thecenterline 2 is about 0.199% at a radius of about 0.57 μm, and themaximum relative refractive index percent of the central core region isabout 0.318% and is located at a radius 6 of about 5.1 μm. The centralcore radius 8, i.e. where the relative refractive index reaches 0%, isabout 7.4 μm. A negative relative refractive index percent annularregion 14 extends from the end of the central core region to a radius 12of about 18.8 μm. The negative relative refractive index percent annularregion shown in FIG. 7 has a minimum negative relative refractive indexpercent of about 0.114% (i.e. a minimum relative refractive index ofabout −0.114%) at a radius of about 15.5 μm. It will be understood thatthe shape of the annular region of negative relative refractive indexpercent can take on shapes other than that illustrated

[0063] The measured results of the optical fiber of FIG. 7 are given inTable 8. TABLE 8 Total Dispersion at 1550 nm (ps/nm-km) 21.3 DispersionSlope at 1550 nm (ps/nm²-km) 0.063 Effective Area (μm²) 166.2 Pin ArrayBend Loss (dB) 1.19 Cabled Cutoff (nm) 1400 Δ_(1,LM (%)) 0.199R_(1,LM)(μm) 0.57 Δ_(1,MAX)(%) 0.318$\frac{\Delta_{1,{LM}}}{\Delta_{1,{MAX}}}$

0.63 R_(1,MAX)(μm) 5.1 R₁(μm) 7.4 $\frac{R_{1,{MAX}}}{R_{1}}$

0.69 $\frac{R_{1,{LM}}}{R_{1}}$

0.03 R_(1,MAX) − R_(1,LM)(μm) 4.53 Δ_(2,MIN)(%) −0.114 R_(2,MN)(μm) 15.5R₂(μm) 18.8 $\frac{R_{2}}{R_{1}}$

2.54$\frac{\Delta_{1,{MAX}} - \Delta_{1,{LM}}}{R_{1,{MAX}} - R_{1,{LM}}}\left( {\% \text{-}{\mu m}^{- 1}} \right)$

0.0263 Mode Field Diameter, MFD (μm) 13.35 32 mm Mandrel, 1 turn, @ 1550nm (dB/m) 0.37 32 mm Mandrel, 1 turn, @ 1610 nm (dB/m) 0.41 Attenuation@ 1310 nm (dB/km) 0.351 Attenuation @ 1380 nm (dB/km) 0.58 Attenuation @1550 nm (dB/km) 0.196 Attenuation @ 1610 nm (dB/km) 0.200 Length (km)5.97

EXAMPLE 8

[0064] An optical fiber was manufactured having a central core region,an annular region, and cladding. The measured refractive index profileof the manufactured fiber is shown by the plot of relative refractiveindex percent versus radius in FIG. 8. The local minimum relativerefractive index percent of the central core region on or near thecenterline 2 is about 0.223% at a radius of about 0.41 μm, and themaximum relative refractive index percent of the central core region isabout 0.282% and is located at a radius 6 of about 5.0 μm. The centralcore radius 8, i.e. where the relative refractive index reaches 0%, isabout 8.2 μm. A negative relative refractive index percent annularregion 14 extends from the end of the central core region to a radius 12of about 17.0 μm. The negative relative refractive index percent annularregion shown in FIG. 8 has a minimum negative relative refractive indexpercent of about 0.154% (i.e. a minimum relative refractive index ofabout −0.154%) at a radius of about 14.8 μm. It will be understood thatthe shape of the annular region of negative relative refractive indexpercent can take on shapes other than that illustrated

[0065] The measured results of the optical fiber of FIG. 8 are given inTable 9. TABLE 9 Total Dispersion at 1550 nm (ps/nm-km) 21.4 DispersionSlope at 1550 nm (ps/nm²-km) 0.067 Effective Area (μm²) 176.5 Pin ArrayBend Loss (dB) 1.33 Cabled Cutoff (nm) 1480 Δ_(1,LM)(%) 0.223R_(1,LM)(μm) 0.41 Δ_(1,MAX)(%) 0.282$\frac{\Delta_{1,{LM}}}{\Delta_{1,{MAX}}}$

0.79 R_(1,MAX)(μm) 5.0 R₁(μm) 8.2 $\frac{R_{1,{MAX}}}{R_{1}}$

0.61 $\frac{R_{1,{LM}}}{R_{1}}$

0.08 R_(1,MAX) − R_(1,LM)(μm) 4.59 Δ_(2,MIN)(%) −0.154 R_(2,MIN)(μm)14.8 R₂(μm) 17.0 $\frac{R_{2}}{R_{1}}$

2.07$\frac{\Delta_{1,{MAX}} - \Delta_{1,{LM}}}{R_{1,{MAX}} - R_{1,{LM}}}\left( {\% \text{-}{\mu m}^{- 1}} \right)$

0.0129 Mode Field Diameter, MFD (μm) 14.2 32 mm Mandrel, 1 turn, @ 1550nm (dB/m) 0.3 32 mm Mandrel, 1 turn, @ 1610 nm (dB/m) 0.2 Attenuation @1310 nm (dB/km) 0.329 Attenuation @ 1380 nm (dB/km) 0.291 Attenuation @1550 nm (dB/km) 0.191 Attenuation @ 1610 nm (dB/km) 0.193 Length (km)11.1

[0066] The agreement between the modeled and measured optical waveguidefiber parameters is good. The manufactured fiber has very high effectivearea and unusually good resistance to bend induced attenuation.

[0067] Thus, an optical fiber is disclosed herein comprising a centralcore region and a clad layer. The central core region is disposed abouta centerline and extending to a radius R₁, and the central core regionhas a local minimum relative refractive index percent Δ_(1, LM) locatedat a radius R_(1, LM) on or near the centerline and a maximum relativerefractive index percent Δ_(1, MAX) located at a radius R_(1, MAX),wherein R_(1, MAX)>R_(1, LM). The clad layer surrounds the central coreregion. The ratio Δ_(1, LM)/Δ_(1, MAX) is greater than 0.65 and lessthan 1.0. The optical fiber exhibits an effective area not less than 115μm² at a wavelength of 1550 nm and exhibits an increase in attenuationinduced by one turn of said optical fiber about a 32 mm diameter mandrelless than about 0.5 dB at a wavelength of 1550 nm. The presence of alocal minimum relative refractive index percent helps to provide alarger effective area, while a gradual increase in relative refractiveindex percent helps to hold down bending loss.

[0068] In one set of preferred embodiment, the clad layer abuts thecentral core region.

[0069] The optical fiber preferably exhibits lateral load bend loss at1550 nm not greater than 1.5 dB/m.

[0070] In one set of preferred embodiments, the ratioΔ_(1, LM)/Δ_(1, MAX) is between 0.6 and 0.9. In another set of preferredembodiments, the ratio Δ_(1, LM)/Δ_(1, MAX) is between 0.7 and 0.85.

[0071] Preferably, the change in relative refractive index percent withrespect to radius between R_(1, LM) and R_(1, MAX) is less than about0.03%-μm⁻¹. In some preferred embodiments, the change in relativerefractive index percent with respect to radius between R_(1, LM) andR_(1, MAX) is between about 0.01%-μm⁻¹ and about 0.03%-μm⁻¹.

[0072] The radial spacing between the maximum and the local minimumrelative refractive index percent of the central core region,R_(1, MAX)−R_(1, LM), is preferably greater than 3 μm, more preferablygreater than 4 μm.

[0073] In one set of preferred embodiments, the ratioR_(1, LM)/R_(1, MAX) is less than about 0.2. In another set of preferredembodiments, the ratio R_(1, LM) /R_(1, MAX) is less than about 0.1.

[0074] Preferably, the ratio R_(1, MAX)/R₁ is greater than about 0.25.In one set of preferred embodiments, the ratio R_(1, MAX)/R₁ is greaterthan about 0.5.

[0075] Preferably, R₁ is between about 6 μm and about 10 μm. In one setof preferred embodiments, R₁ is between about 7 μm and about 9 μm.

[0076] Preferably, Δ_(1, MAX) is less than about 0.4%. In one set ofpreferred embodiments, Δ_(1, MAX) is between about 0.25% and about0.35%.

[0077] Preferably, Δ_(1, LM) is between about 0.10% and about 0.3%.

[0078] Preferably, the relative refractive index percent risesmonotonically from Δ_(1, LM) to Δ_(1, MAX).

[0079] Preferably, relative refractive index of the central core regionis at all points from the centerline to R₁ greater than 0%.

[0080] In a preferred set of embodiments, the optical fiber furthercomprises an annular region disposed between the central core region andthe clad layer, wherein the relative refractive index percent of theannular region is less than 0% and has a minimum relative refractiveindex percent Δ_(2, MIN), and wherein the annular region extends to aradius R₂.

[0081] Preferably, Δ_(2, MIN) is between about −0.05% and about −0.30%.In one set of preferred embodiments, Δ_(2, MIN) is between about −0.10%and about −0.20%.

[0082] Preferably, R₂ is between about 14 μm and about 20 μm.Preferably, the ratio R₂/R₁ is less than about 3.

[0083] In one set of preferred embodiments, the optical fiber exhibitsan effective area not less than 130 μm² at a wavelength of 1550 nm. Inanother set of preferred embodiments, the optical fiber exhibits aneffective area not less than 150 μm² at a wavelength of 1550 nm. In yetanother set of preferred embodiments, the optical fiber exhibits aneffective area not less than 170 μm² at a wavelength of 1550 nm.

[0084] Preferably, the attenuation at a wavelength of 1550 nm is lessthan about 0.21 dB/km, more preferably less than about 0.20 dB/km, andeven more preferably less than about 0.19 dB/km.

[0085] Preferably, the attenuation at a wavelength of 1610 nm is lessthan about 0.20 dB/km.

[0086] Preferably, the attenuation at a wavelength of 1380 nm is lessthan about 0.3 dB/km above the attenuation at a wavelength of 1310 nm.More preferably, the attenuation at a wavelength of 1380 nm is less thanabout 0.32 dB/km. Even more preferably, the attenuation at a wavelengthof 1380 nm is less than the attenuation at a wavelength of 1310 nm.

[0087] Preferably, the attenuation induced by one turn of said opticalfiber about a 32 mm diameter mandrel is less than about 1.0 dB at awavelength of 1610 nm, more preferably less than about 0.5 dB at awavelength of 1610 nm, and even more preferably less than about 0.3 dBat a wavelength of 1610 nm.

[0088] Preferably, the optical fiber has a dispersion of less than 24ps/nm-km at a wavelength of 1550 nm. In one set of preferredembodiments, the optical fiber has a dispersion of greater than 15ps/nm-km and less than 24 ps/nm-km at a wavelength of 1550 nm.

[0089] A particular advantage offered by the refractive index profilesas disclosed herein is that the profiles are quite simple in design andthus are easier to manufacture than those designs having a more complexcore structure. In one embodiment an adjustment of the relativerefractive index percent on centerline allows the resulting opticalwaveguide fiber to simultaneously exhibit large effective area andremarkably good resistance to bend induced attenuation. In those systemswhere higher effective area is desirable, the addition of a singlenegative index annular region can be added.

[0090] All of the exemplary optical fibers disclosed herein weremanufactured with a cladding diameter (i.e. outside diameter of thesilica-based fiber) of 125 μm and a coating, comprised of primary andsecondary coating layers, that resulted in optical fibers having anoutside diameter of 250 μm. The 125 μm diameter cladding, as well as the250 μm optical fiber outside diameter, have become industry standardsizes. While one or more optical properties of an optical fiber may bechanged by changing the cladding diameter and/or the coatingthicknesses, the optical fibers disclosed herein provide large effectiveareas and low microbend losses without resorting to cladding diametersand/or coating thicknesses which deviate from industry standards, i.e.beyond industry accepted tolerances. Accordingly, the optical fibersdisclosed herein preferably have a cladding outside diameter of about125 μm. Furthermore, the optical fibers disclosed herein preferably havean outside coating diameter of 250 μm.

[0091] The refractive index profile designs as disclosed herein can bemade using any of the preform making and drawing techniques known in theart, including modified vapor deposition, outside vapor deposition, orvertical deposition methods. Known consolidation and optionalover-cladding steps can be used to make a preform in accord with theinvention. Standard techniques can be used in the drawing step.

[0092] It will be apparent to those skilled in the art that variousmodifications and variations of the present invention can be madewithout departing from the spirit and scope of the invention. Thus, itis intended that the present invention include the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

We claim:
 1. An optical fiber comprising: a central core region disposedabout a centerline and extending to a radius R₁, the central core regionhaving a local minimum relative refractive index percent Δ_(1, LM)located at a radius R_(1, LM) on or near the centerline and a maximumrelative refractive index percent Δ_(1, MAX) located at a radiusR_(1, MAX), wherein R_(1, MAX)>R_(1, LM); and a clad layer surroundingthe central core region; wherein the ratio Δ_(1, LM)/Δ_(1, MAX) isgreater than 0.65 and less than 1.0; and wherein the optical fiberexhibits an effective area not less than 115 μm² at a wavelength of 1550nm and an increase in attenuation induced by one turn of said opticalfiber about a 32 mm diameter mandrel less than about 0.5 dB at awavelength of 1550 nm.
 2. The optical fiber of claim 1 wherein theattenuation at a wavelength of 1550 nm is less than about 0.21 dB/km. 3.The optical fiber of claim 1 wherein the optical fiber exhibits lateralload bend loss at 1550 nm not greater than 1.5 dB/m.
 4. The opticalfiber of claim 1 wherein the ratio Δ_(1, LM)/Δ_(1, MAX) is between 0.6and 0.9.
 5. The optical fiber of claim 1 wherein the change in relativerefractive index percent with respect to radius between R_(1, LM) andR_(1, MAX) is less than about 0.03%-μm⁻¹.
 6. The optical fiber of claim1 wherein the ratio R_(1, LM)/R_(1, MAX) is less than about 0.2.
 7. Theoptical fiber of claim 1 wherein the ratio R_(1, MAX)/R₁ is greater thanabout 0.25.
 8. The optical fiber of claim 1 wherein R₁ is between about6 μm and about 10 μm.
 9. The optical fiber of claim 1 wherein Δ_(1, MAX)is less than about 0.4%.
 10. The optical fiber of claim 1 wherein therelative refractive index percent rises monotonically from Δ_(1, LM) toΔ_(1, MAX).
 11. The optical fiber of claim 1 wherein relative refractiveindex of the central core region is at all points greater than 0%. 12.The optical fiber of claim 1 further comprising an annular regiondisposed between the central core region and the clad layer, whereinrelative refractive index percent of the annular region less than 0% andhas a minimum relative refractive index percent A_(2, MIN), and whereinthe annular region extends to a radius R₂.
 13. The optical fiber ofclaim 12 wherein Δ_(2, MIN) is between about −0.05% and about −0.30%.14. The optical fiber of claim 1 wherein the optical fiber exhibits aneffective area not less than 130 μm² at a wavelength of 1550 nm.
 15. Theoptical fiber of claim 1 wherein the optical fiber exhibits an effectivearea not less than 150 μm² at a wavelength of 1550 nm.
 16. The opticalfiber of claim 1 wherein the optical fiber exhibits an effective areanot less than 170 μm² at a wavelength of 1550 nm.
 17. The optical fiberof claim 1 wherein the attenuation at a wavelength of 1550 nm is lessthan about 0.19 dB/km.
 18. The optical fiber of claim 1 wherein theattenuation at a wavelength of 1610 nm is less than about 0.20 dB/km.19. The optical fiber of claim 1 wherein the attenuation at a wavelengthof 1380 nm is less than about 0.3 dB/km above the attenuation at awavelength of 1310 nm.
 20. The optical fiber of claim 1 wherein theattenuation induced by one turn of said optical fiber about a 32 mmdiameter mandrel is less than about 1.0 dB at a wavelength of 1610 nm.